The location of a mobile, wireless or wired device is a useful and sometimes necessary part of many services. The precise methods used to determine location are generally dependent on the type of access network and the information that can be obtained from the device. For example, in wireless networks, a range of technologies may be applied for location determination, the most basic of which uses the location of the radio transmitter as an approximation.
Exemplary wireless networks may be a World Interoperability for Microwave Access (“WiMAX”) network, a Long Term Evolution (“LTE”) network, and the like. Generally, WiMAX is intended to reduce the barriers to widespread broadband access deployment with standards-compliant wireless solutions engineered to deliver ubiquitous fixed and mobile services such as VoIP, messaging, video, streaming media, and other IP traffic. LTE is generally a 4G wireless technology and is considered the next in line in the Global System for Mobile Communication (“GSM”) evolution path after Universal Mobile Telecommunications System (“UMTS”)/High-Speed Downlink Packet Access (“HSPDA”) 3G technologies. LTE builds on the 3GPP family including GSM, General Packet Radio Service (“GPRS”), Enhanced Data Rate for Global Evolution (“EDGE”), Wideband Code Division Multiple Access (“WCDMA”), High Speed Packet Access (“HSPA”), etc., and is an all-IP standard like WiMAX. LTE is based on orthogonal frequency division multiplexing (“OFDM”) Radio Access technology and multiple input multiple output (“MIMO”) antenna technology. LTE provides higher data transmission rates while efficiently utilizing the spectrum thereby supporting a multitude of subscribers than is possible with pre-4G spectral frequencies. LTE is all-IP permitting applications such as real time voice, video, gaming, social networking and location-based services. LTE networks may also co-operate with circuit-switched legacy networks and result in a seamless network environment and signals may be exchanged between traditional networks, the new 4G network and the Internet seamlessly. While LTE protocol is being defined in the 3GPP standards as the next generation mobile broadband technology, there is a need for mobile subscriber or user equipment (“UE”) location in LTE networks for compliance with the FCC E-911 requirements and for other location based services. The 3GPP standards have also identified different methods that could be used for positioning of an UE for an evolved-UMTS Terrestrial Radio Access Network (“E-UTRAN”).
A number of applications currently exist within conventional communication systems, such as those supporting GSM, Time Division Multiple Access (“TDMA”), Code Division Multiple Access (“CDMA”), Orthogonal Frequency Division Multiple Access (“OFDMA”) and UMTS technologies, for which location solutions are needed by mobile units, mobile stations, UE or other devices and by other entities in a wireless network. Examples of such applications may include, but are not limited to, GSM positioning and assisted global position system (“A-GPS”) positioning. A-GPS adaptable UE may acquire and measure signals from a number of satellites to obtain an accurate estimate of the UE's current geographic position. GPS-based solutions may offer excellent accuracy, but GPS-based solutions generally suffer from yield issues in indoor environments or in environments that provide a poor line of sight to the open sky in which to best receive GPS satellite transmissions. Furthermore, embedding GPS chipsets into UE may also add an associated cost to the manufacturing of the UE and an associated cost to A-GPS functionality in the respective communications network. Further, some organizations are hesitant to offer a positioning method solely based upon the availability of a satellite network controlled by the United States government. There, however, exists a need in the art to locate UMTS, OFDMA or W-CDMA mobile devices to satisfy FCC E-911 regulations as well as to provide Location Based Services for mobile phone users.
The 3GPP UMTS standard outlines several methods for location including Cell-ID, Enhanced Cell-ID (“E-CID”), A-GPS, Observed Time Difference of Arrival (“OTDOA”), and Uplink Time Difference of Arrival (“U-TDOA”). Cell-ID generally is the simplest method which provides coarse positioning of mobile devices based on a known location of the coverage area centroid of each base station sector. Additionally, A-GPS is a straightforward implementation for network and handset manufacturers due to their legacy in CDMA2000 networks. Likewise, U-TDOA is also a straightforward technique for those skilled in the art and has been widely deployed for other air standards. OTDOA, on the other hand, is confronted with significant implementation challenges for network carriers, due to the fact that the base station timing relationships must be known, or measured, for this technique to be viable. For unsynchronized UMTS networks, where the base station timing is not locked to a common timing source, the 3GPP standard offers the suggestion that base station Location Measurement Units (“LMUs”) or Network Synchronization Units (“NSUs”) may be utilized to recover this timing information. Once the base station timing relationships are measured, the handset measurements of Observed Time Difference (“OTD”) between various base stations may be translated into absolute ranges and range differences from which position can be calculated (e.g., through UE-based or UE-assisted methods).
The UMTS standard offers alternative location solutions for UE location. OTDOA technologies, with or without Idle Period Downlink (“IPDL”), have been developed and integrated into the UMTS standard as optional features to enable location of UEs. However, UMTS carriers have been reluctant to adopt these technologies because carriers had not initially requested these optional features in most UE devices. Additionally, concern may exist regarding the impact OTDOA may have on the operation of a communications network including call quality and network capacity. Because widespread adoption of OTDOA may require modifications in both the base stations and mobile stations, network providers are generally more interested in a solution that operates with existing mobile devices and base stations.
Some prior art systems are mobile appliance-based and determine the position of the mobile appliance by receiving multiple dedicated location signals either from components outside the mobile appliance's communication system, such as satellites and GPS systems or from a network of dedicated land-based antennas. Other prior art geolocation systems that are network overlay, or infrastructure-based, systems use combinations of specific, as opposed to ambiguous, measurements generally from multiple base stations, such as AOA, TOA and TDOA. These specific measurement values may be utilized to solve a set of mathematical equations to determine the location of the mobile appliance.
There is, however, a need in the art to obviate the deficiencies in the prior art and provide methods that use both uplink and downlink signal measurements in an exemplary communications network, such as, but not limited to, a UMTS, LTE network, etc. There is also a need in the art to provide measurements from downlink positioning methods and E-CID methods to determine UE positioning for both synchronous and asynchronous networks.
One embodiment of the present subject matter provides a method of determining the location of a mobile device in a communications network having a plurality of nodes. The method may include receiving observed positioning information for a mobile device from one or more nodes and determining downlink transmission time of a signal from the one or more nodes as a function of the received observed positioning information. Uplink positioning information from the mobile device may be received and a propagation delay determined between a node serving the mobile device and the mobile device as a function of the received uplink positioning information. Downlink timing information from the serving node may then be determined as a function of the determined downlink transmission time and the determined propagation delay. One or more ranges between additional nodes and the mobile device may be determined as a function of the determined downlink transmission time and the determined downlink timing information, and a location of the mobile device estimated as a function the determined one or more ranges and the determined propagation delay.
Another embodiment of the present subject matter may provide a method of determining the location of a mobile device in a communications network having a plurality of nodes, one of the plural nodes serving the device. The method may include receiving observed positioning measurements for a mobile device from the serving node and receiving uplink E-CID positioning measurements from the mobile device. One or more ranges may be determined between ones of the plural nodes and the mobile device as a function of the received observed positioning measurements and the received uplink E-CID positioning measurements, and a geographic location of the mobile device determined as a function the determined one or more ranges.
A further embodiment of the present subject matter provides a method of determining the location of a mobile device in a communications network having a plurality of nodes. The method may include receiving OTDOA measurements for a mobile device from one or more of the plural nodes and receiving uplink E-CID positioning measurements from the mobile device. One or more ranges may be determined between the plural nodes and the mobile device as a function of the received OTDOA measurements and received uplink E-CID positioning measurements. These determined ranges may be adjusted as a function of a metric, and a geographic location of the mobile device determined as a function the adjusted ranges.
These embodiments and many other objects and advantages thereof will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the embodiments.